1. Field of the Invention
The present invention relates to an ignition apparatus for internal combustion engines and in particular to an ignition apparatus of which configuration is simplified to reduce the number of parts of the apparatus.
2. Description of the Prior Art
FIG. 5 shows a configuration of a conventional ignition apparatus for internal combustion engines. In the figure, denoted 1 is a distributor cap, 2 a central electrode disposed at the center of the distributor cap 1, 3 a plurality of side electrodes each disposed at a circumference of the distributor cap 1 in accordance with each cylinder of the engine, 4 a distribution rotor rotatably slidably contacting with the central electrode 2 and selectively connected to the side electrode 3, 5 a high-voltage code connected to the side electrode 3, 6 ion current detecting diodes, 7 a diode assembly including the diodes 6. The diode assembly 7 comprises a diode and resin portion enclosing electrodes and is disposed in accordance with each cylinder of the engine. Reference numeral 8 shows an ignition plug connected to the side electrode 3 by way of the high-voltage code 5 and the diode assembly 7, 9 an engine on which the ignition plug is mounted, 10 a signal generator for detecting a rotation angle of the engine 9, 11 an ion current detecting unit connected to the ion current detecting diodes 6, 12 an ion current flowing route, 13 a computer unit for controlling ignition timing or the like based on output signals from the ion current detecting unit 11. Denoted 14 is a power transistor controlled in accordance with output signals from the computer unit 13. Further, numeral 15 shows an ignition coil of which primary and secondary windings are connected to a collector of the power transistor and the central electrode respectively.
Now, operation of the conventional ignition apparatus for internal combustion engines shown in FIG. 5 will be explained. The computer unit 13 is operated synchronously with the rotation of the internal combustion engine, that is, in response to output signals from the signal generator 10. When an output signal from the computer unit turns off the power transistor, counter electromotive force is generated at the primary winding of the ignition coil 15 to generate negative high voltage. Then, the negative high voltage is applied to the ignition plug by way of the central electrode 2, the side electrode 3, the high-voltage code 5 and the like to ignite the plug 8. In this case, the negative high voltage has no effect on the ion current detecting unit 11 due to the direction of the diode 6. When mixed gas in the cylinder of the engine is burnt after ignition of the ignition plug 6, ion current is generated to be inputted to the ion current detecting unit 11 through an ion current flowing route 12 because the ion current is biased to negative voltage by negative power source of the ion current detecting unit 11. Whether or not the mixed gas is normally burnt in each cylinder of the engine is known by the computer unit through signals transmitted from the ion current detecting unit 11 and rotation angle of the internal combustion engine detected by the signal generator 10.
Since the conventional ignition apparatus for internal combustion engines with a configuration described above is provided with the diode assembly for each cylinder of the engine, production cost of the apparatus increases due to a complicated structure thereof and the layout for the diode assembly becomes difficult due to small engine room adopted in recent years. Moreover, there is another problem that the increased number of parts of the apparatus may decrease reliability of the apparatus.
FIG. 7 shows another embodiment of an ignition apparatus for internal combustion engines conventionally used. In the figure, reference numeral 301 shows an ignition plug and 302 is a connection device including an ion current detecting diode 303. Negative side of the ignition plug 301 is grounded. Further, the other side of the plug is connected to an external connection terminal 305 of an ignition coil unit 304 by way of the connection device 302 and is also connected to negative electrode of a dc power source 307 by way of the ion current detecting diode 303 of the connection device 302 and a resistor 305. A cathode of the ion current detecting diode 303 is grounded through a condenser 308 and a resistor 309. Further, between the condenser 308 and the resistor 309 is provided a terminal 310 to output ion current detecting signals.
The ignition coil unit, which is made of high-voltage material to resist high voltage, includes an ignition coil 311 and a backflow protection diode 312. The ignition coil 311 is connected to a power source by way of a positive terminal 313 at an end of primary winding thereof. Further, the other end of the primary winding of the coil is connected to a collector of the power transistor 315 by way of a negative terminal. An emitter of the power transistor is grounded and a base thereof is connected to an input terminal 316 to which control signals from a control unit (not shown) for controlling fuel injection timing and ignition timing are inputted.
The operation of the conventional ignition apparatus for internal combustion engines shown in FIG. 7 is almost the same as the apparatus shown in FIG. 6, therefore, explanation of the operation is omitted.
Since the conventional ignition apparatus for internal combustion engines shown in FIG. 7 with a configuration described above is separately provided with high-voltage connection device 302 including the ion current detecting diode 303, production cost of the apparatus increases due to a complicated structure thereof and a complicated layout for high-voltage cables.
FIG. 8 shows a configuration of a conventional ignition plug connecting apparatus used for ignition apparatus for internal combustion engines. In the figure, denoted 201 is an ignition plug, 202 a high-voltage code, 203 a connecting member for the ignition plug 201 and the high-voltage code 202, 204 a backflow protection diode, 205 an ion current detecting diode. These diodes 204 and 205 are provided with anodes 204a and 205a, and cathodes 204b and 205b respectively. Numeral 206 shows a conductive member connected to the anodes 204a and 205a. Further, denoted 207 is a connection member for connecting the conductive member 206 and the high-voltage code 202, 208 a housing accommodating the diode 204 and the conductive member 206, 209 a high-voltage code, 210 a connection member for the high-voltage code and the cathode 204b, 211 another connection member for connecting the high-voltage code 209 to a distributor (not shown), and 212 an output signal cable for connecting the cathode 205b to an ion current detecting apparatus (not shown).
Negative high voltage, which is generated at an ignition coil (not shown) connected to the connection member 211 on the distributor side thereof, is applied by way of the diode 204 to the ignition plug 201, thereby fuel gas is ignited. Then, ion current generated by the combustion of the fuel gas is fed to the ion current detecting apparatus by way of the diode 205 to check flameout.
Since the conventional ignition plug connecting apparatus engines has a configuration described above, production cost of the apparatus increases due to the increased number of parts of the apparatus.
Further, wiring for high-voltage codes 202 and 209 is troublesome, especially when the number of cylinders is increased. There is another problem that noise caused by high voltage for ignition is likely to put on a signal line since the high-voltage code 202 is commonly used for the high-voltage ignition and the signal line.